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Postings from May 2002
# New Ticket Created by "Peter Gibbs" # Please include the string: [netlabs #629] # in the subject line of all future correspondence about this issue. # <URL: http://bugs6.perl.org/rt2/Ticket/Display.html?id=629 > Attached patch does some fairly radical things to the memory manager. 1) Cycle counter added to interpreter structure; incremented by opcodes that have something vaguely resembling a function call in their body. 2) Buffer-like objects have their date of birth (cycle counter value) recorded 3) Neonate flag is deprecated; functionality replaced by the above i.e. no buffer header will be freed during the same opcode as it was created 4) Free pool array replaced by a linked list within the arenas 5) Minimum/maximum ratio of memory pool physical size to used size controlled by new tuning parameters (fixed #define's for now) 6) DOD run performed during memory allocation if compaction will not reclaim enough memory The 'function-call like' logic (which is very primitive at present) for adding the cycle count increment into an op's body means that most simple opcodes should not incur additional overhead. Once an op starts calling functions, the additional overhead of a single increment is likely to be minor. After much thought and playing around, this seems to be the best answer to the problem of infant mortality. Dan's suggestion of reversing the logic of DOD runs would work for the pure infant mortality situation (except perhaps for the odd pathological op), but it still leaves problems with the dependency of buffer memory collection on prior dead object detection. These changes do cause a slight performance degradation, but I believe it is worth it for the overall simplification of transparent protection of the newborn. Performance can only be a secondary goal, after correct behaviour. The runaway memory usage of programs like zip and quicksort has hopefully been resolved; I have successfully run zip.pasm against core_ops.c. Note that the neonate flag has not been removed; if this patch is applied, all use of the neonate flag can be removed, followed by the flag itself. The flag is not used in the new GC logic. The problem of having buffer memory move around still remains; that should be addressed shortly. -- Peter Gibbs EmKel Systems